The present invention relates to a fixing device for quickly fastening and releasing a mechanical part that bears on a support base.
Although the invention is not limited to any specific type of mechanical part for fixing to its support base, it relates more particularly to fixing tooling on an associated support base, which tooling needs to be put into place quickly and accurately on the support base, and then fixed thereto in reliable manner. Reference can be made in particular to the tooling fitted to packaging installations, in particular installations for filling or stoppering receptacles. The tooling in such installations conventionally comprises guide bars in the form of curved flat section members associated with star wheels or cylinders having curved notches or recesses serving to drive receptacles so that they are displaced along the conveyor line of the packaging installation.
In existing installations, such tooling is fixed by releasable links of various types. Mention can be made of systems having a simple link of the screw-and-nut type, optionally associated with retractable flanges, or systems using an eccentric, or indeed toggle-type lever systems or other systems relying on elastic deformation.
Document U.S. 4,362,413 discloses a quick fastening device comprising a clamping mechanism of the screw-and-nut type in which the nut has studs co-operating with a facing female part to form a bayonet latching mechanism. The assembly formed in that way is driven via the head of the screw. After the nut has been engaged in the female part, the head of the screw is rotated in the tightening direction, initially entraining the nut so that it rotates until the studs come into abutment. Continued rotation of the head of the screw then gives rise to clamping by the screw being tightened in the nut.
That sequence of movements of the device relies exclusively on the relative values of the resistive forces acting on the screw-and-nut, and also on the female part and the studs, such that if the nut is not properly engaged in the female part, rotating the head of the screw can give rise to tightening even though latching has not been performed properly. In addition, when untightening it is not possible to guarantee that the bayonet mechanism is caused to rotate. That device is therefore designed for providing fastening on a single occasion only.
An object of the invention is to design a fixing device both for fastening and for releasing, and which is both quick and reliable concerning latching and tightening during repeated fastening and release operations.
In addition, when the fixing device is for fitting to packaging installations or other installations concerned with foodstuffs, it is desired that the resulting fixing should be non-dirtying, i.e. free from any external portions presenting particles of pollution such as grease. Finally, to comply with the looked-for requirements of fastening and release operations taking place quickly, accessibility of the drive means and simplicity of the driving operations naturally constitute an object that is particularly desired for the preferred embodiment of the invention.
According to the invention, this problem is resolved by a fixing device for quickly fastening and releasing a mechanical part that bears on a support base, said device comprising a latching mechanism of the bayonet type and an associated clamping mechanism of the screw-and-nut type organized coaxially with said latching mechanism, the two mechanisms being actuated one after the other by actuating a common rotary drive member in the same direction, the device further comprising temporary coupling means interposed between the control member and the latching and clamping mechanisms, and organized in such a manner that over a first angle of rotation of the drive member said drive member is constrained to rotate with the latching mechanism, and that over a second angle of rotation of the drive member, said drive member is released from the latching mechanism and actuates the clamping mechanism.
The temporary coupling means thus ensures that the latching mechanism and the clamping mechanism are implemented in such a manner that those two functions can be performed in the proper order, both during fastening and during release, merely by reversing the control applied to the drive member.
In a particularly advantageous embodiment, the temporary coupling means comprises firstly a ring constrained to rotate with the screw of the clamping mechanism organized between the drive member forming the nut of the clamping mechanism and a fixed head rigidly secured to the mechanical part to be fixed or to the support base, and secondly a coupling member passing in an associated through bore of the ring, said coupling member being partially received either in a blind bore of the drive member over the first angle of rotation of said drive member, or else in an associated blind bore of the fixed head over the second angle of rotation of the drive member. In particular, the coupling member may be constituted by a steel ball. It is then advantageous to provide for the ring and the fixed head to carry complementary abutment and/or indexing means serving to define the first angle of rotation of the drive member, preferably over a short angle of the quarter-turn type.
Also preferably, the ring and the drive member carry complementary means for rotary drive that act during unscrewing of said drive member. The release process can then take place in extremely simple manner without the need to use any kind of external tool.
It is also advantageous to provide for the ring to be constrained to rotate with the screw by indexed linking that allows relative movement along the direction of the axis of the screw.
When the fixing device is one in which the fixed head is rigidly secured to the mechanical part to be fixed, it is advantageous to provide for the latching mechanism to comprise a rod that is coaxial with and secured to the screw of the clamping mechanism, said rod having a free end with projecting portions passing through a matching cutout in the support plate.
In a variant, when the device is one in which the fixed head is rigidly secured to the support base, it is advantageous to provide for the latching mechanism to comprise a rod that is coaxial with and secured to the screw of the clamping mechanism, said rod having a free end with projecting portions that pass through a matching cutout in the mechanical part to be fixed.
In another advantageous variant of the fixing device, in which the fixed head is rigidly secured to the support base, provision is made for the ring of the temporary coupling means to present projecting peripheral portions for latching the mechanical part to be fixed which bears on the support base, and centered on said fixed head by means of a matching cutout in said part, said ring then forming a component of the latching mechanism.
In which case it is advantageous for the external profiles of the ring and of the drive member to be included within the profile of the cutout of the mechanical part to be fixed, thereby enabling said part to be put into place or extracted while it is in the corresponding angular position and without it being necessary to remove the drive member.